MoPac lane switch to mean 10 months of slower traffic

Northbound MoPac between West Sixth Street and Enfield Road will see a shift and a lane reduction late in November.

The south end of the MoPac Boulevard toll lane project, the section between the lake and Enfield Road designed to have two tunnels laboriously cut under the existing lanes, was always expected to be most painful phase of construction for motorists.

That pain will arrive around Thanksgiving, officials say.

To speed construction of a toll lane tunnel, northbound MoPac in a short section will be reduced temporarily to two lanes.

That’s when northbound MoPac just north of Lady Bird Lake, which has had three lanes for the past five years, will be reduced to two lanes and, for about 10 months, abruptly swerve to the east and then back to the west a few hundred yards later. The change, which will allow workers to excavate a substantial area and then build much of the tunnel from West Chavez Street to the northbound express lane, is expected to further clog traffic on a section of the freeway that already slows to a stop-and-start crawl in both the morning and evening commute times, officials said.

“We are acutely aware of the delay and the the pain that we’re going to inflict on the traveling public,” said Wes Burford, director of engineering for the Central Texas Regional Mobility Authority, which is building the toll lanes and will operate them. “And we’re trying to do that for the least amount of time possible, in the most efficient way. But we’re under no delusions that this won’t cause backups.”

If all goes as planned — and much has not gone that way on a project that initially was to have been done a month ago — the short detour and lane reduction should be complete by the end of September next year. The overall project, based on the latest estimate from the mobility authority and its contractor CH2M, should be done by the end of 2016 or early in 2017.

The overall point of the $200 million North MoPac project is to install a single toll lane on each side from south of Enfield to about Parmer Lane, a distance of 11 miles. Those lanes will be on the inside of MoPac, nearest the center median (or in the southern several miles, the Union Pacific railroad). The challenge for designers was how to directly connect those toll lanes to and from the most direct route to downtown, West Cesar Chavez, providing a speed incentive for more people to pay for that alternative.

That meant either building short bridges that would go over the existing free MoPac lanes, or under them with tunnels. Officials chose the tunnel approach. But rather than boring underground to create them, the plan is to dig trenches, pave the floor of the trench and then build what amounts to concrete walls and a ceiling. Then the trenches will be filled in and the surface paved over, once again restoring the free lanes to their original orientation.

Work on the southbound tunnel began this summer, and while some exit access was disrupted, no lanes were lost. For the time being, drivers can only access the Lake Austin Boulevard exit from the West Cesar Chavez exit ramp, though eventually those will return to being two separate exits. Still, the construction project has caused no lane reductions southbound, as MoPac already narrows to two lanes south of the exit to West Cesar Chavez.

Northbound MoPac between West Sixth Street and Enfield Road will see a shift and a lane reduction late in November.

But on the northbound side, the Texas Department of Transportation, which owns and operates the free lanes of MoPac, in 2010 had restriped the bridge over the Union Pacific railroad to increase it from two lanes to three. This temporary change in effect restores the pre-2010 design.

Under this short-term change, drivers coming from downtown (including on West Sixth Street) temporarily will have their own northbound MoPac lane to enter, increasing the road back to three lanes at that point. Currently, those downtown commuters have to merge into MoPac lanes already carrying traffic, and that arrangement will resume when the project is completed.

“I think it’s going to help us, the people coming from Sixth and Cesar Chavez,” said Wayne Blackard, who lives downtown and commutes to a programming job on RM 2222. “But it’s going to back things up on the bridge back to the south. It’s going to go back like it was in 2010.”

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